"It's f***ing lit, Jimmy."

In a clip for the episode which aired today, a love-struck Davidson appeared alongside Robert Pattinson, telling the host, "I feel like I won a contest," adding, "It's so sick. It's fucking lit, Jimmy."

The 24-year-old told Fallon he’s even had strangers approach him on the street congratulating him on the big news.

"Some dude came up to me and was like, ‘Yo man, you gave me hope,'" he laughed.

Grande -- who has been inseparable from her fiancé since they began dating in May -- reportedly watched on proudly from the audience, with an insider telling E! News, “She had a huge smile on her face the entire time and was constantly clapping.”

The singer even posted a sweet video of the SNL star to her Instagram story, captioning the clip, “A perfect specimen”.

Since rumours of their pending nuptials broke, the couple have been spotted out and about together and were seen enjoying a dinner date on Tuesday night at Chef Bobby Flay's restaurant Gato in New York City.

The loved-up couple out and about in NYC. Image: Getty.

"They looked pretty loved up," a source told E! News. "They held hands in and out of the car. Pete appeared to help her get out of the car and down the step exiting with those giant heels she had on. Like a gentleman. Very sweet."